The parents of a teenager who disappeared in 1991 have urged anyone with information about the location of her body to search their conscience and contact police.

John and Marilyn Payne hope a “life-changing” £100,000 reward from an anonymous funder will encourage potential witnesses to help to trace their daughter’s remains.

Young mother Nicola Payne, then aged 18, was last seen as she walked across waste ground in the Wood End area of Coventry on December 14 1991.

The latest search is taking place at the city’s Coombe Country Park, using ground-penetrating radar by private company Specialist Group International.

Police scoured the same area in November 2016 after receiving “credible” new information concerning the sighting of two men in the area on the day Nicola disappeared.

Speaking to the media at Coventry’s Little Park Street Police Station, Mr and Mrs Payne vowed to “never, ever give up” hope of finding Nicola, who is believed to have been abducted and killed.

Mrs Payne said: “You’ve always got to keep positive and hopeful because that will help make things happen – that’s just what I believe.

John and Marilyn Payne (Joe Giddens/PA)

“You think that people that do these things are bad people – and yes they are – but everybody has to have a conscience and at some point you really should look deep into what it’s telling you – you will have family, children of your own.

“How would you feel?

“We’ve never ever given up, never stopped searching. Everything has always revolved around having her found. I will always try and stay positive that we are going to get our answer.”

Mrs Payne said she believed potential witnesses may be “terrified” at the prospect of coming forward, but would be able to stay safe due to the size of the reward being offered.

Mr Payne added: “You just keep praying that one day she will be found. We hope somebody will come forward because we want to know her whereabouts.”

Asked what message he would give to anyone with information to help the inquiry, he added: “Think in your conscience, do what you can and just let us know.”

Police officers search an area of Coombe Country Park in Coventry after receiving new witness information relating to the disappearance of Nicola Payne (Joe Giddens/PA)

Superintendent Tom Chisholm, of West Midlands Police, said officers were waiting to speak to a new potential witness identified by investigative reporter Mark Williams-Thomas, who has offered support to the inquiry.

The officer said: “I do believe that at the time there were local people who could have come forward that didn’t for whatever reason – it may have been fear or otherwise.

“There is a significant reward now. The priority for the family and for myself is to recover Nicola’s body to allow her to be laid to rest.

“Clearly I will always be looking for forensic potential from anything that I find, but the main thrust of today is to recover Nicola’s body for her parents.”

Two men aged 51 were acquitted of murdering Miss Payne by a jury in November 2015 after a trial at Birmingham Crown Court.